Quite simply, the Senate rules don’t clearly say that you can filibuster a change to the rules about filibusters.

Eliminating filibusters would be a major historic change to the way the Senate operates and one of the biggest changes to it since the 17th Amendment, which allowed direct election of senators in 1913.

The filibuster in its original form dates back to the 1830s and it allows a senator (or a group of senators) to delay a vote on procedures, legislation, judicial nominees and executive branch nominees by taking the Senate floor and physically holding it as long as possible.

Like actor Jimmy Stewart in the film “Mr. Smith Goes To Washington,” a senator would speak continuously—sometimes off-the-cuff, other times, reading from a phone book—in a public protest about a vote.

“Talking filibusters” are rare nowadays because the Senate changed its rules to allow for “silent filibusters.” This happens when a senator tells his or her floor leader that they wish to filibuster a vote. At that point, at least 60 senators have to agree to override the filibuster in what is called a cloture vote.

The frequent use of silent filibusters caused a big stir in January when Senate majority leader Harry Reid threatened to use a little-known move called the “nuclear option” or “constitutional option” to re-write the Senate rule book, and kill the filibuster entirely.

Minority leader Mitch McConnell and senators from both parties brokered a compromise to save the filibuster in January. But now the two sides are set to meet in the Old Senate building on Monday night in a last-ditch attempt to reach another compromise before the nuclear option is deployed this week.

According to the Congressional Research Service, there is no direct Senate rule that permits filibustering. It is the combination of two rules in paragraph 1(a) of Rule XIX that allow for the procedure.

“This is essentially all that the Senate’s rules have to say about the right to speak on the floor, so the rule is just as important for what it does not say as for what it does say. The lack of discretion by the chair in recognizing Senators and the lack of time limits on debate combine to create the possibility of filibusters by debate,” says the CRS.

This whole nuclear/constitutional filibuster scenario nearly happened back in 2005, when the Republicans controlled the Senate and felt frustrated by Democratic filibustering.

At the time, Senate majority leader Bill Frist weighed the nuclear or constitutional option, but cooler heads prevailed. (Here is a link to a detailed article on Salon.com from that time period that spells out the filibuster battle.)

The process would work like this. A senator would raise a “point of order” or an objection on the Senate floor, or it could be raised by the presiding officer. For example, the point of order could be about the constitutionality of a filibuster to block President Barack Obama’s nominations to the National Labor Relations Board.

“The plan most often discussed has been to raise a point of order asserting that the Senate must be able to reach a vote on nominations (or procedural changes) in order to exercise effectively its constitutional ‘advice and consent’ power (or rulemaking power),” the CRS said in 2005.

The president officer of the Senate would then hear an appeal objecting to the whole idea of killing the filibuster.

“Opponents of the ruling could appeal, and could attempt to filibuster to prevent a vote on the appeal, but the Senate could confirm the ruling by adopting a nondebatable motion to table the appeal,” the CRS said.

The tool of using a motion to put aside objections to killing the filibuster is how the Democrats could leverage 51 votes in the Senate to make history. That procedural vote only requires a simple majority, and not the two-thirds majority required to change the Senate’s standing rules.

The CRS does point out several other options using points of order, motions and votes to kill the filibuster, and it remains to be seen exactly how the Democrats would act.

Whether its history they really want to make is another question. The CRS was quite clear the “nuclear option” was called that for a reason.

“Under most conditions, the Senate might be unable to reach a vote on a procedural question that would institute consideration limits, except by setting aside the principle that the chair adheres to precedent, or that the rules remain always in effect. Once these principles were set aside, however, it might become possible for any voting majority of the Senate to institute further procedural changes in other subsequent situations,” it said.

In other words, a simple majority could be used to rewrite other parts of the Senate rule book, which would change the basic pretext of how the Senate has operated for decades.

For now, Reid is expected to push for an end to filibusters on executive-branch appointments only. On Monday, he downplayed the move in a speech.

“This is really a moment in history that circumstances dictate a change. Minor change. Again, no big deal,” Reid said at the Center for American Progress. “Filibusters are not part of the Constitution, it’s something that senators developed on their own,” he added.

On Sunday, McConnell stated an argument that will be repeated this week.

“The reason they call this the ‘nuclear option’ because it is breaking the rules of the Senate to change the rules of the Senate,” McConnell said on NBC’s “Meet the Press.”

Scott Bomboy is the editor-in-chief of the National Constitution Center.